A sublimation heat transfer method forms printed images by heating a heat transfer sheet applied with a sublimation dye by a thermal head and the like, thereby transferring the sublimation dye onto a sublimation transfer image receiver which comes in contact with the heat transfer sheet.
The dyeable resin to be used for the dyeable layer of said sublimation transfer image receiver has been conventionally one mainly containing a saturated polyester, as disclosed in, for example, Japanese Patent Unexamined Publication Nos. 107885/1982, 64899/1985, 258790/1986 and 105679/1987.
While a sublimation transfer image receiver using a saturated polyester as the dyeable resin can provide high quality images superior in gradation and color reproduction, it is becoming insufficient in dye sensitivity due to the acceleration of the printing speed of a printer. Then, the dyeing sensitivity of the image receiver has been improved by adding various plasticizers and/or additives to a saturated polyester resin. However, plasticizers and additives have poor compatibility with polyester resins, and particularly when a printed image receiver is preserved for an extended period of time, the printed images tend to become blurred or plasticizers and additives precipitate on the surface of the image receiver with the lapse of time.
While the dyeing sensitivity has been improved by lowering the glass transition temperature of a polyester through modification of the resin skeleton, this method exerts adverse influence on heat resistance, thus resulting in blurred images or changes in the color of dye after dyeing.
An object of the present invention is to overcome such conventional defects and provide a polyester resin suitable as a dyeable resin for a sublimation transfer image receiver, which can make images highly sensitive without using a plasticizer or additive.
Another object of the present invention is to provide a sublimation transfer image receiver containing the above-mentioned dyeable resin.